If you load a multi-volume (4D) file, MultiTracer will default to display the average value across all loaded volumes in the main display window (and in the any orthogonal windows set to display the 4D volume). In addition two new windows not seen with 3D volumes will appear. One of these provides a graphical display of the time series of the voxel currently under the cursor. The title bar of the window will provide the raw value range represented in the display.
The other window will consist of a table listing the image number (starting with zero for the lowest loaded volume), a "contrast" value, the file name and the full path name for the file. Editing the contrast and then pressing the "Apply" button will alter the weighting of the corresponding volume in the image displayed in the main window. The contrast values can be negative, allowing them to be used to create an image showing activation magnitudes in fMRI tasks (it may be necessary to increase the image intensity to see small differences). The "File" menu associated with this window allows contrasts to be saved to or loaded from external text files. The "Define" menu provides some useful defaults. For example, choosing the "First image only" option will display only the first volume (its contrast will be set to one and all other' to zero). Pressing the "+" and "-" buttons in the contrast window will shift the contrasts to the next or preceeding volume respectively, allowing the displayed volume to be sequentially advanced through the full time series to look for artifacts or movement.
The contrast weightings in the contrast window will also determine the shading that appears behind the graphical time series display.
If multiple 4D volumes are loaded, time series and contrast windows will be created for each time series
©2001-2012 Roger P. Woods, M.D.
Modified: August 27, 2012